Editing IPCC:AR6/WGIII/Chapter-14 (section)

== 14.4 Supplementary Means and Mechanisms of Implementation ==

<div id="h1-5-siblings" class="h1-siblings"></div>

As discussed above, the Paris Agreement sets in place a new framework for international climate policy albeit one that is embedded in the wider climate regime complex ( [[#Coen--2020|Coen et al. 2020]] ). Whereas international governance had earlier assumed centre stage, the Paris Agreement recognises the salience of domestic politics in the governance of climate change ( [[#Kinley--2020|Kinley et al. 2020]] ). The new architecture also provides more flexibility for recognising the benefits of working in diverse forms and groups and allows for more decentralised ‘polycentric’ forms of governance ( [[#Jordan--2015|Jordan et al. 2015]] ; [[#Victor--2016|Victor 2016]] ). The next two sections address this complementarity between the Paris Agreement and other agreements and institutions.

The Paris Agreement identifies a number of pathways, or means of implementation, towards accomplishing rapid mitigation and the achieving of its temperature goal: finance; capacity building; technology and innovation; and cooperative approaches and markets (Sections 14.3.2.7–14.3.2.10 above). In this section, we examine each of these means and mechanisms of implementation, and the agreements and institutions lying outside of the Paris Agreement that contribute to each. In the following section, 14.5, we examine the agreements and institutions playing other governance roles: regulating activities in particular sectors; linking climate mitigation with other activities such as adaptation; and stimulating and coordinating the actions of non-state actors at a global scale.

Figure 14.3 maps out the interlinkages described in the text of Sections 14.4 and 14.5. It is an incomplete list, but illustrates clearly that across multiple types of governance, there are multiple instruments or organisations with activities connected to the different governance roles associated with the Paris Agreement and the UNFCCC more generally.

<div id="figure-14-3" class="Basic-Text-Frame"></div>

[[File:153085f068d3e98c02221cf9bad9bbff IPCC_AR6_WGIII_Figure_14_3.png]]

'''Figure 14.3 | Climate governance beyond the UNFCC''' '''C.''' The figure shows those relationships, marked in blue, between international governance activities, described in the text, that relate to activities of the UNFCCC and Paris Agreement.

<div id="14.4.1" class="h2-container"></div>

<span id="finance"></span>
=== 14.4.1 Finance ===

<div id="h2-11-siblings" class="h2-siblings"></div>

International cooperation on climate finance is underpinned by various articles of the UNFCCC including Articles 4.3, 4.4, 4.5, 4.7 and 11.5 ( [[#UNFCCC--1992|UNFCCC 1992]] ). This was further amplified through the commitment by developed countries in the Copenhagen Accord and the Cancun Agreements to mobilise jointly through various sources USD100 billion yr –1 by 2020 to meet the needs of the developing countries ( [[#UNFCCC--2010b|UNFCCC 2010b]] ). This commitment was made in the context of meaningful mitigation action and transparency of implementation. As mentioned in [[#14.3.2.8|Section 14.3.2.8]] , in the Paris Agreement the binding obligation on developed country Parties to provide financial resources to assist developing country Parties applies to both mitigation and adaptation ( [[#UNFCCC--2015a|UNFCCC 2015a]] , Art. 9.1). In 2019, climate finance provided and mobilised by developed countries was in the order of USD79.6 billion, coming from different channels including bilateral and multilateral channels, and also through mobilisation of the private sector attributable to these channels ( [[#OECD--2021|OECD 2021]] ). A majority (two-thirds) of these flows targeted mitigation action exclusively (Chapter 15). These estimates, however, have been criticised on various grounds, including that they are an overestimate and do not represent climate-specific net assistance only; that in grant equivalence terms the order of magnitude is lower; and the questionable extent of transparency of information on mobilised private finance, as well as the direction of these flows ( [[#Carty--2020|Carty et al. 2020]] ). On balance, such assessments need to be viewed in the context of the original commitment, the source of the data and the evolving guidance, and modalities and procedures from the UNFCCC processes. As mentioned in Chapter 15, the measurement of climate finance flows continues to face definitional, coverage and reliability issues, despite progress made by various data providers and collators ( [[IPCC:Wg3:Chapter:Chapter-15#15.3.2|Section 15.3.2]] ).

The multiplicity of actors providing financial support has resulted in a fragmented international climate finance architecture as indicated in [[#14.3.2.8|Section 14.3.2.8]] . It is also seen as a system which allows for speed, flexibility and innovation ( [[#Pickering--2017|Pickering et al. 2017]] ). However, the system is not yet delivering adequate flows given the needs of developing countries ( [[#14.3.2.8|Section 14.3.2.8]] ). An early indication of these self-assessed needs is provided in the conditional NDCs. Of the 136 conditional NDCs submitted by June 2019, 110 have components or additional actions conditioned on financing support for mitigation and 79 have components or additional actions for support for adaptation ( [[#Pauw--2020|Pauw et al. 2020]] ). While the Paris Agreement did not explicitly countenance conditionality for actions in developing countries, it is generally understood that the ambition and effectiveness of climate ambition in these countries is dependent on financial support ( [[#Voigt--2016b|Voigt and Ferreira 2016b]] ).

<div id="14.4.1.1" class="h3-container"></div>

<span id="bilateral-finance"></span>
==== 14.4.1.1 Bilateral Finance ====

<div id="h3-19-siblings" class="h3-siblings"></div>

The Paris Agreement and the imperative for sustainable development reinforce the need to forge strong linkages between climate and development ( [[#Fay--2015|Fay et al. 2015]] ). This in turn has highlighted the urgent need for greater attention to the relationship between development assistance and finance, and climate change ( [[#Steele--2015|Steele 2015]] ).

The UNFCCC website cites some 20 bilateral development agencies providing support to climate change programmes in developing countries ( [[#UNFCCC--2020a|UNFCCC 2020a]] ). These agencies provide a mix of development cooperation, policy advice and support and financing for climate change projects. Since the year 2000, the OECD Development Assistance Committee has been tracking trends in climate-related development finance and assistance. The amount of bilateral development finance with climate relevance has increased substantially since 2000 ( [[#OECD--2019a|OECD 2019a]] ). For 2019, it was reported to be USD28.8 billion in direct finance and USD2.6 billion through export credit agencies. Further, another USD34.1 billion of the climate finance provided through multilateral channels is attributable to the developed countries ( [[#OECD--2021|OECD 2021]] ). The OECD methodology has been critiqued as it uses Rio markers, the limitations of which could lead to erroneous reporting and assessment of finance provided as well as of the mitigation outcome ( [[#Michaelowa--2011b|Michaelowa and Michaelowa 2011b]] ; [[#Weikmans--2019|Weikmans and Roberts 2019]] ). This issue is to be addressed through the modalities, procedures and guidance under the Enhanced Transparency Framework of the Paris Agreement ( [[#14.3.2.4|Section 14.3.2.4]] ), through the mandate to the Subsidiary Body for Scientific and Technological Advice (SBSTA) to develop common tabular formats for the reporting of information on, ''inter alia'' , financial support provided, mobilised and received ( [[#UNFCCC--2019k|UNFCCC 2019k]] ). Until then, the Biennial Assessment Report prepared by the Standing Committee on Finance provides the best available information on financial support.

<div id="14.4.1.2" class="h3-container"></div>

<span id="multilateral-finance"></span>
==== 14.4.1.2 Multilateral Finance ====

<div id="h3-20-siblings" class="h3-siblings"></div>

Multilateral development banks (MDBs) comprise six global development banks: the European Investment Bank, International Fund for Agricultural Development, International Investment Bank, New Development Bank, OPEC Fund for International Development, and the World Bank Group; six regional development banks: the African Development Bank, Asian Development Bank, Asian Infrastructure Investment Bank, European Bank for Reconstruction and Development, Inter-American Development Bank, and the Islamic Development Bank; and 13 sub-regional development banks: the Arab Bank for Economic Development in Africa, Arab Fund for Economic and Social Development, Black Sea Trade and Development Bank, Caribbean Development Bank, Central American Bank for Economic Integration, Development Bank of the Central African States, Development Bank of Latin America, East African Development Bank, Eastern and Southern African Trade and Development Bank, Economic Cooperation Organization Trade and Development Bank, Economic Community of West African States Bank for Investment and Development, Eurasian Development Bank, and the West African Development Bank. Together they play a key role in international cooperation at the global, regional and sub-regional levels because of their growing mandates and proximity to policymakers ( [[#Engen--2018|Engen and Prizzon 2018]] ). For many, climate change is a growing priority and for some, because of the needs of the regions or sub-regions in which they operate, climate change is embedded in many of their operations.

In 2015, 20 representative MDBs and members of the International Development Finance Club unveiled five voluntary principles to mainstream climate action in their investments: commitment to climate strategies, managing climate risks, promoting climate smart objectives, improving climate performance and accounting for their own actions ( [[#World%20Bank--2015a|World Bank 2015a]] ; [[#Institute%20for%20Climate%20Economics--2017|Institute for Climate Economics 2017]] ). The members subscribing to these principles had grown to 44 as of January 2020. Arguably, it is only through closer linkages between climate and development that significant inroads can be made in addressing climate change. MDBs can play a major role through the totality of their portfolios ( [[#Larsen--2018|Larsen et al. 2018]] ).

The MDBs as a cohort have been collaborating and coordinating in reporting on climate financing following a commitment made in 2012 at the UN Conference on Sustainable Development in Rio de Janeiro ( [[#Inter-American%20Development%20Bank--2012|Inter-American Development Bank 2012]] ). This has engendered other forms of collaboration among the MDBs, including, commitments to: collectively total at least USD65 billion annually by 2025 in climate finance, with USD50 billion for low- and middle-income economies; to mobilise a further USD40 billion annually by 2025 from private sector investors, including through the increased provision of technical assistance, use of guarantees, and other de-risking instruments; to help clients deliver on the goals of the Paris Agreement; to build a transparency framework on the impact of MDBs’ activities; and to enable clients to move away from fossil fuels ( [[#Asian%20Development%20Bank--2019|Asian Development Bank 2019]] ). While the share of MDBs in direct climate financing is small, their role in influencing national development banks and local financial institutions, and leveraging and crowding in private investments in financing sustainable infrastructure, is widely recognised ( [[#NCE--2016|NCE 2016]] ). However, with this recognition there is also an exhortation to do more to align with the goals of the Paris Agreement, including a comprehensive examination of their portfolios beyond investments that directly support climate action to also enabling the long-term net zero GHG emissions trajectory ( [[#Larsen--2018|Larsen et al. 2018]] ; [[#Cochran--2019|Cochran and Pauthier 2019]] ). Further, a recent assessment has shown that MDBs perform relatively better in mobilising other public finance than private co-financing ( [[#Thwaites--2020|Thwaites 2020]] ). In addition, the banks have launched or are members of significant initiatives such as the Climate and Clean Air Coalition to reduce emissions of shortlived climate pollutants, the Carbon Pricing Leadership Coalition, the Coalition for Climate Resilient Investment and the Coalition of Finance Ministers for Climate Action. These help to spur action at different levels, from economic analysis to carbon financing, and convenors of finance and development ministers for climate action, with leadership of many of these initiatives led by the World Bank.

The multilateral climate funds also have a role in the international climate finance architecture. This includes, as mentioned in [[#14.3.2.8|Section 14.3.2.8]] , those established under the UNFCCC’s financial mechanism, its operating entities, the Global Environment Facility (GEF), which also manages two special funds, the Special Climate Change Fund and the Least Developed Countries Fund; and the Green Climate Fund (GCF), also an operating entity of the financial mechanism which in 2015, was given a special role in supporting the Paris Agreement. The GCF aims to provide funding at scale, balanced between mitigation and adaptation, using various financial instruments including grants, loans, equity, guarantees or others to activities that are aligned with the priorities of the countries compatible with the principle of country ownership ( [[#GCF--2011|GCF 2011]] ). The GCF faces many challenges. While some see the GCF as an opportunity to transform and rationalise what is now a complex and fragmented climate finance architecture with insufficient resources and overlapping remits ( [[#Nakhooda--2014|Nakhooda et al. 2014]] ), others see it as an opportunity to address the frequent tensions which arise between mitigation-focused transformation and national priorities of countries. This tension is at the heart of the principle of country ownership and the need for transformational change ( [[#Winkler--2016|Winkler and Dubash 2016]] ). Leveraging private funds and investments by the public sector and taking risks to unlock climate action are also expressed strategic aims of the GCF.

The UN system is also supporting climate action through much-needed technical assistance and capacity building, which is complementary to the financial flows insofar as it enables countries with relevant tools and methodologies to assess their needs, develop national climate finance roadmaps, establish relevant institutional mechanisms to receive support and track it, enhance readiness to access financing, and include climate action across relevant national financial planning and budgeting processes ( [[#UN--2017a|UN 2017a]] ). The United Nations Development Programme (UNDP) is the largest implementer of climate action among the UN Agencies, with others, such as the Food and Agriculture Organization (FAO), United Nations Environment Programme (UNEP), United Nations Industrial Development Organisation (UNIDO), and United Nations Office for South-South Cooperation (UNOSSC), providing relevant support.

The current architecture of climate finance is one that is primarily based on north-south, developed-developing country dichotomies. The Paris Agreement, however, has clearly recognised the role of climate finance flows across developing countries, thereby enhancing the scope of international cooperation ( [[#Voigt--2016b|Voigt and Ferreira 2016b]] ). Estimates of such flows, though, are not readily available. According to one estimate in 2020 the flows among non-OECD countries were of the order of USD29 billion ( [[#CPI--2021|CPI 2021]] ).

<div id="14.4.1.3" class="h3-container"></div>

<span id="private-sector-financing"></span>
==== 14.4.1.3 Private Sector Financing ====

<div id="h3-21-siblings" class="h3-siblings"></div>

There is a growing recognition of the importance of mobilising private sector financing including for climate action ( [[#World%20Bank--2015b|World Bank 2015b]] ; [[#Michaelowa--2020b|Michaelowa et al. 2020b]] ). An early example of the mobilisation of the private sector in a cooperative mode for mitigation outcomes is evidenced from the Clean Development Mechanism of the Kyoto Protocol and the linking with the European Union’s Emissions Trading System, both triggered by relevant provisions in the Kyoto Protocol ( [[#14.4.4|Section 14.4.4]] ) and lessons learned from this are relevant for development of market mechanisms in the post Paris Agreement period ( [[#Michaelowa--2019b|Michaelowa et al. 2019b]] ). In 2019 and 2020, on average for the two years, public and private climate financing was on the order of USD632 billion, of which USD310 billion originated from the private sector. However, as much as 76% of the (overall) finance stayed in the country of origin. This trends holds true also for private finance ( [[#CPI--2021|CPI 2021]] ). Figure 14.4 depicts the international climate finance flows totalling USD161 billion reported in 2020, about 19% of which were private flows. For (international) mitigation financing flows of USD116 billion, the share provided by private sources was 24%.

<div id="figure-14-4" class="Basic-Text-Frame"></div>

[[File:405398cd66d5c2c8753191963e521953 IPCC_AR6_WGIII_Figure_14_4.png]]

'''Figure 14.4 | International finance flows.''' Total international climate financial flows for 2020 were USD161 billion. By comparison, public sector bilateral and multilateral finance in 2017 for fossil fuel development, including gas pipelines, was roughly USD4 billion. Part (a) disaggregates total financial flows according to public and private sources, and indicates the breakdown between mitigation on the one hand, and adaptation and multiple objectives on the other, within each source. Part (b) disaggregates total financial flows according to intended purpose, namely mitigation or adaptation and multiple objectives, and disaggregates each type according to source. Part (c) provides additional detail on the relative contributions of different public and private sources. Sources: data from [[#CPI--2021|CPI 2021]] ; [[#OECD--2021|OECD 2021]] .

Foreign direct investments and their greening are seen as a channel for increasing cooperation. An assessment of the greenfield foreign direct investment in different sectors shows the growing share of renewable energy at USD92.2 billion (12% of the volume and 38% of the number of projects) ( [[#FDI%20Intelligence--2020|FDI Intelligence 2020]] ). Coal, oil and gas sectors maintain the top spot for capital investments globally. Over the last decade there is growing issuance of green bonds with non-financial private sector issuance gaining ground ( [[#Almeida--2020|Almeida 2020]] ). While it is questionable if green bonds have a significant impact on shifting capital from non-sustainable to sustainable investments, they do incentivise the issuing organisations to enhance their green ambition and have led to an appreciation within capital markets of green frameworks and guidelines and signalled new expectations ( [[#Maltais--2020|Maltais and Nykvist 2020]] ). In parallel, institutional investors including pension funds are seeking investments that align with the Paris Agreement ( [[#IIGCC--2020|IIGCC 2020]] ). However, the readiness of institutional investors to make this transition is arguable ( [[#OECD--2019b|OECD 2019b]] ; [[#Ameli--2020|Ameli et al. 2020]] ). This evidence suggests that international private financing could play an important role but this potential is yet to be realised (Chapter 15).

<div id="14.4.2" class="h2-container"></div>

<span id="science-technology-and-innovation"></span>
=== 14.4.2 Science, Technology and Innovation ===

<div id="h2-12-siblings" class="h2-siblings"></div>

Science, technology and innovation are essential for the design of effective measures to address climate change and, more generally, for economic and social development ( [[#de%20Coninck--2015a|de Coninck and Sagar 2015a]] ). The OECD finds that single countries alone often cannot provide effective solutions to today’s global challenges, as these cross national borders and affect different actors ( [[#OECD--2012|OECD 2012]] ). [[#Madani--2020|Madani (2020)]] shows how conflict, including international sanctions, can reduce science and innovation capacity, which is not evenly distributed, particularly across the developed and the developing world. For this reason, many countries have introduced strategies and policies to enhance international cooperation in science and technology ( [[#Chen--2019|Chen et al. 2019]] ). Partnerships and international cooperation can play a role in establishing domestic innovation systems, which enable more effective science and technology innovation ( [[#de%20Coninck--2015b|de Coninck and Sagar 2015b]] ,a).

International cooperation in science and technology occurs across different levels, with a growing number of international cooperation initiatives aimed at research and collaborative action in technology development. [[#Weart--2012|Weart (2012)]] finds that such global efforts are effective in advancing climate change science due to the international nature of the challenge. Global research programmes and institutions have also provided the scientific basis for major international environmental treaties. For example, the Long-Range Transboundary Air Pollution Convention and the Montreal Protocol were both informed by scientific assessments based on collaboration and cooperation of scientists across several geographies ( [[#Andresen--2000|Andresen et al. 2000]] ). Furthermore, the Global Energy Assessment (GEA) provided the scientific basis and evidence for the 2030 Agenda for Sustainable Development, in particular SDG 7 to ensure access to affordable, reliable and sustainable modern energy for all ( [[#GEA--2012|GEA 2012]] ). The GEA drew on the expertise of scientists from over 60 countries and institutions. Several other platforms exist to provide scientists and policymakers an opportunity for joint research and knowledge sharing, such as The World in 2050, an initiative that brings together scientists from some 40 institutions from around the world to provide the science for SDG and Paris Agreement implementation ( [[#TWI2050--2018|TWI2050 2018]] ).

Non-state actors are also increasingly collaborating internationally. Such collaborations, referred to as international cooperative initiatives (ICIs), bring together multi-stakeholder groups across industry, communities, and regions, and operate both within and outside the UNFCCC process. [[#Lui--2021|Lui et al. (2021)]] find that such initiatives could make a major contribution to global emissions reduction, [[#Bakhtiari--2018|Bakhtiari (2018)]] finds that the impact on greenhouse gas reduction of these initiatives is hindered due to a lack of coordination between ICIs, overlap with other activities conducted by the UNFCCC and governments, and a lack of monitoring systems to measure impact. Increasing the exchange of information between ICIs, enhancing monitoring systems, and increasing collaborative research in science and technology would help address these issues ( [[#Boekholt--2009|Boekholt et al. 2009]] ; [[#Bakhtiari--2018|Bakhtiari 2018]] ).

At the level of research institutes, there has been a major shift to a more structured and global type of cooperation in research; [[#Wagner--2017|Wagner et al. (2017)]] found significant increases in both the proportion of papers written by author teams from multiple countries and in the number of countries participating in such collaboration, over the time period 1990–2013. Although only a portion of these scientific papers address the issue of climate change specifically, this growth of scientific collaboration across borders provides a comprehensive view of the conducive environment in which climate science collaboration has grown.

However, there are areas in which international cooperation can be strengthened. Both the Paris Agreement and the 2030 Agenda for Sustainable Development call for more creative forms of international cooperation in science that help bridge the science and policy interface, and provide learning processes and places to deliberate on possible policy pathways across disciplines on a more sustainable and long-lasting basis. Scientific assessments, such as the IPCC and Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) offer this possibility, but processes need to be enriched for this to happen more effectively ( [[#Kowarsch--2016|Kowarsch et al. 2016]] ).

A particular locus for international cooperation on technology development and innovation is found within institutions and mechanisms of the UN climate regime. The UNFCCC, in Article 4.1(c), calls on ‘all Parties’ to ‘promote and cooperate in the development, application and diffusion, including transfer, of technologies, practices and processes that control, reduce or prevent anthropogenic emissions of greenhouse gases’ and places responsibility on developed country Parties to ‘take all practicable steps to promote, facilitate and finance, as appropriate, the transfer of, or access to environmentally sound technologies and know-how to other Parties, particularly developing country Parties, to enable them to implement the provisions of the Convention’ ( [[#UNFCCC--1992|UNFCCC 1992]] , Art. 4.5). The issue of technology development and transfer has continued to receive much attention in the international climate policy domain since its initial inclusion in the UNFCCC in 1992 – albeit often overshadowed by dominant discourses around market-based mechanisms – and its role in reducing GHG emissions and adapting to the consequences of climate change ‘is seen as becoming ever more critical’ ( [[#de%20Coninck--2015a|de Coninck and Sagar 2015a]] ). Milestones in the development of international cooperation on climate technologies under the UNFCCC have included: (i) the development of a technology transfer framework and establishment of the Expert Group on Technology Transfer (EGTT) under the SBSTA in 2001; (ii) recommendations for enhancing the technology transfer framework put forward at the Bali COP in 2007 and creation of the Poznan strategic programme on technology transfer under the GEF; and (iii) the establishment of the Technology Mechanism by the COP in 2010 as part of the Cancun Agreements ( [[#UNFCCC--2010b|UNFCCC 2010b]] ). The Technology Mechanism is presently the principal avenue within the UNFCCC for facilitating cooperation on the development and transfer of climate technologies to developing countries ( [[#UNFCCC--2015b|UNFCCC 2015b]] ). As discussed in [[#14.3.2.9|Section 14.3.2.9]] above, the Paris Agreement tasks the Technology Mechanism also to serve the Paris Agreement ( [[#UNFCCC--2015b|UNFCCC 2015b]] , Art. 10.3).

The Technology Mechanism consists of the Technology Executive Committee (TEC) (replacing the EGTT), as its policy arm, and the Climate Technology Centre and Network (CTCN), as its implementation arm ( [[#UNFCCC--2015b|UNFCCC 2015b]] ). The TEC focuses on identifying and recommending policies that can support countries in enhancing and accelerating the development and transfer of climate technologies ( [[#UNFCCC--2020b|UNFCCC 2020b]] ). The CTCN facilitates the transfer of technologies through three core services: (i) providing technical assistance at the request of developing countries; (ii) creating access to information and knowledge on climate technologies; and (iii) fostering collaboration and capacity building ( [[#CTCN--2020a|CTCN 2020a]] ). The CTCN ‘network’ consists of a diverse set of climate technology stakeholders from academic, finance, non-government, private sector, public sector, and research entities, together with more than 150 National Designated Entities, which serve as CTCN national focal points. Through its network, the CTCN seeks to mobilise policy and technical expertise to deliver technology solutions, capacity-building and implementation advice to developing countries ( [[#CTCN--2020b|CTCN 2020b]] ). At the Katowice UNFCCC Conference of the Parties in 2018, the TEC and CTCN were requested to incorporate the technology framework developed pursuant to Article 10 of the Paris Agreement into their respective workplans and programmes of work ( [[#UNFCCC--2019f|UNFCCC 2019f]] ).

The Joint Annual Report of the TEC and CTCN for 2019 indicated that, as of July 2019, the CTCN had engaged with 93 developing country Parties regarding a total of 273 requests for technical assistance, including 11 multi-country requests. Nearly three-quarters (72.9%) of requests received by the CTCN had a mitigation component, with two-thirds of those mitigation requests related to either renewable energy or energy efficiency. Requests for decision-making or information tools are received most frequently (28% of requests), followed by requests for technology feasibility studies (20%) and technology identification and prioritisation (18%) ( [[#TEC%20and%20CTCN--2019|TEC and CTCN 2019]] ).

The CTCN is presently funded from ‘various sources, ranging from the [UNFCCC] Financial Mechanism to philanthropic and private sector sources, as well as by financial and in-kind contributions from the co-hosts of the CTCN and from participants in the Network’ ( [[#TEC%20and%20CTCN--2019|TEC and CTCN 2019]] , para. 97). [[#Oh--2020b|Oh (2020b)]] describes the institution as ‘mainly financially dependent on bilateral donations from developed countries and multilateral support’. Nevertheless, inadequate funding of the CTCN poses a problem for its effectiveness and capacity to contribute to implementation of the Paris Agreement. A 2017 independent review of the CTCN identified ‘limited availability of funding’ as a key constraint on its ability to deliver services at the expected level and recommended that ‘[b]etter predictability and security over financial resources will ensure that the CTCN can continue to successfully respond to its COP mandate and the needs and expectations of developing countries’ (Ernst &amp; Young 2017, para. 84). The 2019 Joint Report of the TEC and CTCN indicates that resource mobilisation for the Network remains a challenge ( [[#TEC%20and%20CTCN--2019|TEC and CTCN 2019]] , pp. 23–24).

The importance of ‘financial support’ for strengthening cooperative action on technology development and transfer was recognised in Article 10.6 of the Paris Agreement. The technology framework established by the Paris Rulebook specifies actions and activities relating to the thematic area of ‘support’ as including: (i) enhancing the collaboration of the Technology Mechanism with the Financial Mechanism; (ii) identifying and promoting innovative finance and investment at different stages of the technology cycle; (iii) providing enhanced technical support to developing country Parties, in a country-driven manner, and facilitating their access to financing for innovation, enabling environments and capacity building, developing and implementing the results of TNAs, and engagement and collaboration with stakeholders, including organisational and institutional support; and (d) enhancing the mobilisation of various types of support, including pro bono and in-kind support, from various sources for the implementation of actions and activities under each key theme of the technology framework.

Notwithstanding the technology framework’s directive for enhanced collaboration of the Technology and Financial Mechanisms of the UNFCCC, linkages between them, and particularly to the GCF, continue to engender political contestation between developing and developed countries ( [[#Oh--2020b|Oh 2020b]] ). Developing countries sought to address concerns over the unsustainable funding status of the CTCN by advocating linkage through a funding arrangement or financial linkage, whereas developed countries favour the design of an institutional linkage maintaining the different and separate mandates of the CTCN and the GCF ( [[#Oh--2020a|Oh 2020a]] ,b). With no resolution reached, the UNFCCC COP requested the Subsidiary Body for Implementation, at its fifty-third session, to take stock of progress in strengthening the linkages between the Technology Mechanism and the Financial Mechanism with a view to recommending a draft decision for consideration and adoption by the Glasgow COP, scheduled for 2021 ( [[#UNFCCC--2019l|UNFCCC 2019l]] ).

<div id="14.4.3" class="h2-container"></div>

<span id="capacity-building-1"></span>
=== 14.4.3 Capacity Building ===

<div id="h2-13-siblings" class="h2-siblings"></div>

International climate cooperation has long focused on supporting developing countries in building capacity to implement climate mitigation actions. While there is no universally agreed definition of capacity building and the UNFCCC does not define the term ( [[#Khan--2020|Khan et al. 2020]] ), elements of capacity building can be discerned from the Convention’s provisions on education and training programmes ( [[#UNFCCC--1992|UNFCCC 1992]] , Art. 6), as well as the reference in Article 9(2)(d) to the SBSTA providing support for ‘endogenous capacity-building in developing countries’.

Capacity building is generally conceived as taking place at three levels: individual (focused on knowledge, skills and training), organisational/institutional (focusing on organisational performance and institutional cooperation) and systemic (creating enabling environments through regulatory and economic policies ( [[#Khan--2020|Khan et al. 2020]] ; [[#UNFCCC--2021b|UNFCCC 2021b]] ). In its annual synthesis report for 2018, the UNFCCC secretariat compiled information submitted by Parties on the implementation of capacity building in developing countries, highlighting cooperative and regional activities on NDCs, including projects to build capacity for implementation, workshops related to transparency under the Paris Agreement and collaboration to provide coaching and training ( [[#UNFCCC--2019h|UNFCCC 2019h]] ). A number of developing country Parties also highlighted their contributions to South–South cooperation (discussed further in [[#14.5.1.4|Section 14.5.1.4]] ), and identified capacity-building projects undertaken with others (e.g., capacity-building for risk management in Latin America and the Caribbean, improving capacity for measurement, reporting and verification through the Alliance of the Pacific and a climate action package launched by Singapore).

Beyond the UNFCCC, other climate cooperation and partnership activities on capacity building include climate-related bilateral cooperation and those organised by the OECD, IFDD (Francophonie Institute for Sustainable Development), UNDP National Communications Support Programme, UNEP and the World Bank.

Climate-related bilateral cooperation provides important human and institutional capacity building support for climate change actions and activities in developing countries, particularly through developed countries’ bilateral cooperation structures, such as the French Development Agency (AFD), the German Development Agency (The Deutsche Gesellschaft für Internationale Zusammenarbeit – GIZ), the Japanese International Cooperation Agency (JICA) and others.

There are also a number of regional cooperative structures with capacity-building components, including ClimaSouth, Euroclima+, the UN-REDD Programme, the Caribbean Regional Strategic Programme for Resilience, the Caribbean Climate Online Risk and Adaptation Tool, a project on accelerating low carbon and resilient society realisation in the Southeast Asian region, the World Health Organisation’s Global Salm-Surv network, the Red Iberoamericana de Oficinas de Cambio Climático network and the Africa Adaptation Initiative. Many climate-related capacity-building initiatives, including those coordinated or funded by international or regional institutions, are implemented at the national and sub-national levels, often with the involvement of universities, consultancy groups and civil society actors.

It is also noted that comprehensive support is provided by the GCF to developing countries (GCF, 2020). This support is made available and accessible for all developing countries through three different GCF tools: the Readiness Programme, the Project Preparation Facility, and the funding of transformative projects and programmes. The goal of the Readiness Programme is to strengthen institutional capacities, governance mechanisms, and planning and programming competencies in support of developing countries’ transformational long-term climate policies (GCF, 2020). Despite a decades-long process of capacity-building efforts under many development and environmental regimes, including the UNFCCC, progress has been uneven and largely unsuccessful in establishing institution-based capacity in developing countries ( [[#Robinson--2018|Robinson 2018]] ). In an effort to improve capacity-building efforts within the UNFCCC, in 2015, the Paris Committee on Capacity-building (PCCB) was established by the COP decision accompanying the Paris Agreement as the primary body for enhancing capacity-building efforts, including by improving coherence and coordination in capacity-building activities ( [[#UNFCCC--2016a|UNFCCC 2016a]] , para. 71). The activities of the Committee include the provision of guidance and technical support on climate change training and capacity building, raising awareness and sharing climate information and knowledge. During 2020, the PCCB was able, despite the COVID-19 situation, to hold its fourth meeting, implement and assess its 2017–2020 work plan, and develop and agree on its future roadmap (2021–2024) ( [[#UNFCCC%20Subsidiary%20Body%20for%20Implementation--2020|UNFCCC Subsidiary Body for Implementation 2020]] ). Non-governmental organisations such as the Coalition on Paris Agreement Capacity-building provide expert input to the PCCB.

Quantifying the contribution of capacity-building efforts to climate mitigation is acknowledged to be ‘difficult, if not impossible’ ( [[#Hsu--2019a|Hsu et al. 2019a]] ). Nonetheless, such activities ‘may play a valuable role in building a foundation for future reductions’ by providing ‘necessary catalytic linkages between actors’ ( [[#Hsu--2019a|Hsu et al. 2019a]] ).

<div id="14.4.4" class="h2-container"></div>

<span id="cooperative-mechanisms-and-markets"></span>
=== 14.4.4 Cooperative Mechanisms and Markets ===

<div id="h2-14-siblings" class="h2-siblings"></div>

In theory, trading carbon assets can reduce the costs of global climate mitigation, by helping facilitate abatement of greenhouse gases at least-cost locations. This could help countries ratchet up their ambitions more than in a situation without such mechanisms ( [[#Mehling--2018|Mehling et al. 2018]] ), particularly if mechanisms are scaled up from projects and programmes ( [[#Michaelowa--2019b|Michaelowa et al. 2019b]] ). Progress as to developing such mechanisms has however so far been moderate and uneven.

Of the three international market-based mechanisms under the 1997 Kyoto Protocol discussed in [[#14.3.2.7|Section 14.3.2.7]] , and in previous IPCC reports, only the CDM or a similar mechanism may have a role to play under the Paris Agreement, although the precise terms are yet to be decided.

Article 6, also discussed in [[#14.3.2.7|Section 14.3.2.7]] , is the main framework to foster enhanced cooperation within the Paris Agreement. Although there is an emerging global landscape of activities based on Article 6 ( [[#Greiner--2020|Greiner et al. 2020]] ), such as the bilateral treaty signed under the framework of Article 6 in October 2020 by Switzerland and Peru, the possibilities of bilateral cooperation are yet to be fully exploited. As discussed above, adequate accounting rules are key to the success of Article 6. Sectoral agreements are also a promising cooperative mechanism, as discussed in [[#14.5.2|Section 14.5.2]] . In fact, both bilateral and sectoral agreements have the potential to enhance the ambition of the Parties involved and can eventually serve as building blocks towards more comprehensive agreements ( [[#14.2.2|Section 14.2.2]] ).

A relevant and promising new development is the international linkage of existing regional or national emissions trading systems (ETS). Several ETS are now operational in different jurisdictions, including the EU, Switzerland, China, South Korea, New Zealand, Kazakhstan and several US states and Canadian provinces ( [[#Wettestad--2018|Wettestad and Gulbrandsen 2018]] ). More systems are in the pipeline, including Mexico and Thailand ( [[#ICAP--2019|ICAP 2019]] ). The link between the EU and Switzerland entered into force in January 2020 and other linkages are being negotiated. Scholars analyse the potential benefits of these multilateral linkages and demonstrate that these can be significant ( [[#Doda--2019|Doda et al. 2019]] ; [[#Doda--2017|Doda and Taschini 2017]] ). Over time, the linkages of national emissions trading systems can be seen as building blocks to a strategic enlargement of international cooperation ( [[#Caparrós--2017|Caparrós and Péreau 2017]] ; [[#Mehling--2019|Mehling 2019]] ). The World Bank has emerged as an important lynchpin and facilitator of knowledge-building and sharing of lessons about the design and linking of carbon markets, through initiatives such as the Partnership for Market Readiness, Networked Carbon Markets and the Carbon Pricing Leadership Coalition ( [[#Wettestad--2021|Wettestad et al. 2021]] ).

However, it is important to distinguish between theory and practice. The practice of ETS linking so far demonstrates a few attempts that did not result in linkages due to shifts of governments and political preferences (for instance the process between the EU and Australia, and Ontario withdrawing from the Western Climate Initiative) ( [[#Bailey--2018|Bailey and Inderberg 2018]] ). It is worth noting that the linking of carbon markets raises problems of distribution of costs and loss of political control and hence does not offer a politically easy alternative route to a truly international carbon market. Careful, piecemeal and incremental linking may be the most feasible approach forward ( [[#Green--2014|Green et al. 2014]] ; [[#Gulbrandsen--2019|Gulbrandsen et al. 2019]] ). It is premature for any serious assessment of the practice of ETS linking to be conducted. Environmental effectiveness, transformative potential, economic performance, institutional strength and even distributional outcomes can potentially be significant and positive if linking is done carefully ( [[#Doda--2017|Doda and Taschini 2017]] ; [[#Mehling--2018|Mehling et al. 2018]] ; [[#Doda--2019|Doda et al. 2019]] ), but are all marginal if one focuses on existing experiences ( [[#Spalding-Fecher--2012|Spalding-Fecher et al. 2012]] ; [[#Haites--2016|Haites 2016]] ; [[#Schneider--2017|Schneider et al. 2017]] ; [[#La%20Hoz%20Theuer--2019|La Hoz Theuer et al. 2019]] ; [[#Schneider--2019|Schneider et al. 2019]] ).

<div id="14.4.5" class="h2-container"></div>

<span id="international-governance-of-srm-and-cdr"></span>
=== 14.4.5 International Governance of SRM and CDR ===

<div id="h2-15-siblings" class="h2-siblings"></div>

While Solar Radiation Modification (SRM) and carbon dioxide removal (CDR) were often referred to as ‘geoengineering’ in earlier IPCC reports and in the literature, IPCC SR1.5 started to explore SRM and CDR more thoroughly and to highlight the differences between – but also within – both approaches more clearly. This section assesses international governance of both SRM and CDR, recognising that CDR, as a mitigation option, is covered elsewhere in this report, whereas SRM is not. [[IPCC:Wg3:Chapter:Chapter-12|Chapter 12]] of this report covers the emerging national, sub-national and non-state governance of CDR, while Chapters 6, 7 and 12 also assess the mitigation potential, risks and co-benefits of some CDR options. Chapters 4 and 5 of AR6 WGI assess the physical climate system and biogeochemical responses to different SRM and CDR methods. Cross-Working Group Box 4 on SRM (AR6 WGII, Chapter 16; and Cross-Working Group Box 4 in this chapter) gives a brief overview of Solar Radiation Modification methods, risks, benefits, ethics and governance.

<div id="Cross-Working Group Box 4 | Solar Radiation Modification " class="h2-container"></div>

<span id="cross-working-group-box-4-solar-radiation-modification"></span>
=== Cross-Working Group Box 4 | Solar Radiation Modification ===

<div id="h2-16-siblings" class="h2-siblings"></div>

'''Authors:''' Govindasamy Bala (India), Heleen de Coninck (the Netherlands), Oliver Geden (Germany), Veronika Ginzburg (the Russian Federation), Katharine J. Mach (the United States of America), Anthony Patt (Switzerland), Sonia I. Seneviratne (Switzerland), Masahiro Sugiyama (Japan), Christopher H. Trisos (South Africa), Maarten van Aalst (the Netherlands)

Proposed Solar Radiation Modification schemes

This cross-working group box assesses Solar Radiation Modification (SRM) proposals, their potential contribution to reducing or increasing climate risk, as well as other risks they may pose (categorised as risks from responses to climate change in the IPCC AR6 risk definition in 1.2.1.1), and related perception, ethics and governance questions.

SRM refers to proposals to increase the reflection of shortwave radiation (sunlight) back to space to counteract anthropogenic warming and some of its harmful impacts ( [[#de%20Coninck--2018|de Coninck et al. 2018]] ) (AR6 WGI Chapters 4 and 5). A number of SRM options have been proposed, including: stratospheric aerosol interventions (SAI), marine cloud brightening (MCB), ground-based albedo modifications (GBAM), and ocean albedo change (OAC). Although not strictly a form of SRM, cirrus cloud thinning (CCT) has been proposed to cool the planet by increasing the escape of longwave thermal radiation to space and is included here for consistency with previous assessments ( [[#de%20Coninck--2018|de Coninck et al. 2018]] ). SAI is the most-researched proposal. Modelling studies show SRM could reduce surface temperatures and potentially ameliorate some climate change risks (with more confidence for SAI than other options), but SRM could also introduce a range of new risks.

There is high agreement in the literature that for addressing climate change risks, SRM cannot be the main policy response to climate change and is, at best, a supplement to achieving sustained net zero or net negative CO 2 emission levels globally ( [[#de%20Coninck--2018|de Coninck et al. 2018]] ; [[#MacMartin--2018|MacMartin et al. 2018]] ; [[#Buck--2020|Buck et al. 2020]] ; [[#National%20Academies%20of%20Sciences%20Engineering%20and%20Medecine--2021|National Academies of Sciences Engineering and Medecine 2021]] ). SRM contrasts with climate change mitigation activities, such as emissions reductions and CDR, as it introduces a ‘mask’ to the climate change problem by altering the Earth’s radiation budget, rather than attempting to address the root cause of the problem, which is the increase in GHGs in the atmosphere. In addition, the effects of proposed SRM options would only last as long as a deployment is maintained – for example, requiring a yearly injection of aerosols in the case of SAI as the lifetime of aerosols in the stratosphere is one to three years ( [[#Niemeier--2011|Niemeier et al. 2011]] ) or continuous spraying of sea salt in the case of MCB as the lifetime of sea salt aerosols in the atmosphere is only about 10 days – which contrasts with the long lifetime of CO 2 and its climate effects, with global warming resulting from CO 2 emissions likely remaining at a similar level for a hundred years or more ( [[#MacDougall--2020|MacDougall et al. 2020]] ) and long-term climate effects of emitted CO 2 remaining for several hundreds to thousands of years ( [[#Solomon--2009|Solomon et al. 2009]] ).

Which scenarios?

The choice of SRM deployment scenarios and reference scenarios is crucial in assessment of SRM risks and its effectiveness in attenuating climate change risks ( [[#Keith--2015|Keith and MacMartin 2015]] ; [[#Honegger--2021a|Honegger et al. 2021a]] ). Most climate model simulations have used scenarios with highly stylised large SRM forcing to fully counteract large amounts of warming in order to enhance the signal-to-noise ratio of climate responses to SRM ( [[#Kravitz--2015|Kravitz et al. 2015]] ; [[#Sugiyama--2018a|Sugiyama et al. 2018a]] ; [[#Krishnamohan--2019|Krishnamohan et al. 2019]] ).

The effects of SRM fundamentally depend on a variety of choices about deployment ( [[#Sugiyama--2018b|Sugiyama et al. 2018b]] ), including: its position in the portfolio of human responses to climate change (e.g., the magnitude of SRM used against the background radiative forcing), governance of research and potential deployment strategies, and technical details (latitude, materials, and season, among others, see AR6 WGI Chapter 4.6.3.3). The plausibility of many SRM scenarios is highly contested and not all scenarios are equally plausible because of socio-political considerations ( [[#Talberg--2018|Talberg et al. 2018]] ), as with, for example, CDR ( [[#Fuss--2014|Fuss et al. 2014]] , 2018). Development of scenarios and their selection in assessments should reflect a diverse set of societal values with public and stakeholder inputs ( [[#Sugiyama--2018a|Sugiyama et al. 2018a]] ; [[#Low--2020|Low and Honegger 2020]] ), as depending on the focus of a limited climate model simulation, SRM could look grossly risky or highly beneficial ( [[#Pereira--2021|Pereira et al. 2021]] ).

In the context of reaching the long-term global temperature goal of the Paris Agreement, there are different hypothetical scenarios of SRM deployment: early, substantial mitigation with no SRM, more limited or delayed mitigation with moderate SRM, unchecked emissions with total reliance on SRM, and regionally heterogeneous SRM. Each scenario presents different levels and distributions of SRM benefits, side effects, and risks. The more intense the SRM deployment, the larger is the likelihood for the risks of side effects and environmental risks (e.g., [[#Heutel--2018|Heutel et al., 2018]] ). Regional disparities in climate hazards may result from both regionally-deployed SRM options such as GBAM, and more globally uniform SRM such as SAI ( [[#Jones--2018|Jones et al. 2018]] ; [[#Seneviratne--2018|Seneviratne et al. 2018]] ). There is an emerging literature on smaller forcings of SAI to reduce global average warming, for instance, to hold global warming to 1.5°C or 2°C alongside ambitious conventional mitigation ( [[#Jones--2018|Jones et al. 2018]] ; [[#MacMartin--2018|MacMartin et al. 2018]] ), or bring down temperature after an overshoot

( [[#Tilmes--2020|Tilmes et al. 2020]] ). If emissions reductions and CDR are deemed insufficient, SRM may be seen by some as the only option left to ensure the achievement of the Paris Agreement’s temperature goal by 2100.

SRM risks to human and natural systems and potential for risk reduction

Since AR5, hundreds of climate modelling studies have simulated effects of SRM on climate hazards ( [[#Kravitz--2015|Kravitz et al. 2015]] ; [[#Tilmes--2018|Tilmes et al. 2018]] ). Modelling studies have shown SRM has the potential to offset some effects of increasing GHGs on the global and regional climate, including the increase in frequency and intensity of extremes of temperature and precipitation, melting of Arctic sea ice and mountain glaciers, weakening of Atlantic meridional overturning circulation, changes in frequency and intensity of tropical cyclones, and decrease in soil moisture (AR6 WGI, Chapter 4). However, while SRM may be effective in alleviating anthropogenic climate

'''Cross-Working Group Box 4, Table 1 | SRM options and their potential climate and non-climate impacts.''' '''Description, potential climate impacts, potential impacts on human and natural systems, and termination effects of a number of SRM options: stratospheric aerosol interventions (SAI), marine cloud brightening (MCB), ocean albedo change (OAC), ground-based albedo modifications (GBAM), and cirrus cloud thinning (CCT).'''

{| class="wikitable"
|-
| SRM option

| SAI

| MCB

| OAC

| GBAM

| CCT

|-
| Description

| Injection of reflective aerosol particles directly into the stratosphere or a gas which then

converts to aerosols that reflect sunlight

| Spraying sea salt or other particles in marine clouds, making them more reflective

| Increase surface albedo of the ocean (e.g., by creating microbubbles or placing reflective foam on the surface)

| Whitening roofs, changes in land use management (e.g., no-till farming, bioengineering to make crop leaves more reflective), desert albedo enhancement, covering glaciers with reflective sheeting

| Seeding to promote nucleation of cirrus clouds, reducing optical thickness and cloud lifetime to allow more outgoing longwave radiation to escape to space

|-
| Potential climate impacts ''other than reduced warming''

| Change precipitation and runoff pattern; reduced temperature and precipitation extremes; precipitation reduction in some monsoon regions; decrease in direct and increase in diffuse sunlight at surface; changes to stratospheric dynamics and chemistry; potential

delay in ozone hole recovery; changes in surface ozone and UV radiation

| Change in land–sea contrast in temperature and precipitation, regional precipitation and runoff changes

| Change in land–sea contrast in temperature and precipitation, regional precipitation and runoff changes.

| Changes in regional precipitation pattern, regional extremes and regional circulation

| Changes in temperature and precipitation pattern, altered regional water cycle, increase in sunlight reaching the surface

|-
| Potential impacts on human and natural systems

| Changes in crop yields, changes in land and ocean ecosystem productivity, acid rain (if using sulphate), reduced risk of heat stress to corals

| Changes in regional ocean productivity, changes in crop yields, reduced heat stress for corals, changes in ecosystem productivity on land, sea salt deposition over land

| Unresearched

| Altered photosynthesis and carbon uptake and side effects on biodiversity

| Altered photosynthesis and carbon uptake

|-
| Termination effects

| Sudden and sustained termination would result in rapid warming, and abrupt changes to water cycle. Magnitude of termination depends on the degree of warming offset.

| Sudden and sustained

termination would result in rapid warming, and abrupt changes to water cycle. Magnitude of termination depends on the degree of warming offset.

| Sudden and sustained

termination would result in rapid warming. Magnitude of termination depends on the degree of warming offset.

| GBAM can be maintained over several years without major termination effects because of its regional scale of application.

Magnitude of termination depends on the degree of warming offset.

| Sudden and sustained

termination would result in rapid warming. Magnitude of termination depends on the degree of warming offset.

|-
| References (also see main text of this box)

| [[#Visioni--2017|Visioni et al. (2017)]]

[[#Tilmes--2018|Tilmes et al. (2018)]]

[[#Simpson--2019|Simpson et al. (2019)]]

| [[#Latham--2012|Latham et al. (2012)]]

[[#Ahlm--2017|Ahlm et al. (2017)]]

[[#Stjern--2018|Stjern et al. (2018)]]

| [[#Evans--2010|Evans et al. (2010)]]

[[#Crook--2015|Crook et al. (2015)]]

| [[#Davin--2014|Davin et al. (2014)]]

[[#Crook--2015|Crook et al. (2015)]]

[[#Zhang--2016|Zhang et al. (2016)]]

[[#Field--2018|Field et al. (2018)]]

[[#Seneviratne--2018|Seneviratne et al. (2018)]]

| [[#Storelvmo--2014|Storelvmo and Herger (2014)]]

[[#Crook--2015|Crook et al. (2015)]]

[[#Jackson--2016|Jackson et al. (2016)]]

[[#Duan--2020|Duan et al. (2020)]]

[[#Gasparini--2020|Gasparini et al. (2020)]]

|}

warming either locally or globally, it would not maintain the climate in a present-day state nor return the climate to a pre-industrial state (climate averaged over 1850–1900) (AR6 WGI, Box 1.2) in all regions and in all seasons even when used to fully offset the global mean warming ( ''high confidence'' ) (AR6 WGI Chapter 4). This is because the climate forcing and response to SRM options are different from the forcing and response to GHG increase. Because of these differences in climate forcing and response patterns, the regional and seasonal climates of a world with a global mean warming of 1.5°C or 2°C achieved via SRM would be different from a world with similar global mean warming but achieved through mitigation ( [[#MacMartin--2018|MacMartin et al. 2018]] ). At the regional scale and seasonal timescale there could be considerable residual climate change and/or overcompensating change (e.g., more cooling, wetting or drying than just what’s needed to offset warming, drying or wetting due to anthropogenic greenhouse gas emissions), and there is ''low confidence'' in understanding of the climate response to SRM at the regional scale (AR6 WGI, Chapter 4).

SAI implemented to partially offset warming (e.g., offsetting half of global warming) may have potential to ameliorate hazards in multiple regions and reduce negative residual change, such as drying compared to present-day climate, that are associated with fully offsetting global mean warming ( [[#Irvine--2020|Irvine and Keith 2020]] ), but may also increase flood and drought risk in Europe compared to unmitigated warming ( [[#Jones--2021|Jones et al. 2021]] ). Recent modelling studies suggest it is conceptually possible to meet multiple climate objectives through optimally designed SRM strategies (WGI, Chapter 4). Nevertheless, large uncertainties still exist for climate processes associated with SRM options (e.g., aerosol-cloud-radiation interaction) (AR6 WGI, Chapter 4) ( [[#Kravitz--2020|Kravitz and MacMartin 2020]] ).

Compared with climate hazards, many fewer studies have examined SRM risks – the potential adverse consequences to people and ecosystems from the combination of climate hazards, exposure and vulnerability – or the potential for SRM to reduce risk ( [[#Curry--2014|Curry et al. 2014]] ; [[#Irvine--2017|Irvine et al. 2017]] ). Risk analyses have often used inputs from climate models forced with stylised representations of SRM, such as dimming the sun. Fewer have used inputs from climate models that explicitly simulated injection of gases or aerosols into the atmosphere, which include more complex cloud-radiative feedbacks. Most studies have used scenarios where SAI is deployed to hold average global temperature constant despite high emissions.

There is ''low confidence'' and large uncertainty in projected impacts of SRM on crop yields due in part to a limited number of studies. Because SRM would result in only a slight reduction in CO 2 concentrations relative to the emissions scenario without SRM (AR6 WGI, Chapter 5), the CO 2 fertilisation effect on plant productivity is nearly the same in emissions scenarios with and without SRM. Nevertheless, changes in climate due to SRM are likely to have some impacts on crop yields. A single study indicates MCB may reduce crop failure rates compared to climate change from a doubling of CO 2 pre-industrial concentrations ( [[#Parkes--2015|Parkes et al. 2015]] ). Models suggest SAI cooling would reduce crop productivity at higher latitudes compared to a scenario without SRM by reducing the growing season length, but benefit crop productivity in lower latitudes by reducing heat stress ( [[#Pongratz--2012|Pongratz et al. 2012]] ; [[#Xia--2014|Xia et al. 2014]] ; [[#Zhan--2019|Zhan et al. 2019]] ). Crop productivity is also projected to be reduced where SAI reduces rainfall relative to the scenario without SRM, including a case where reduced Asian summer monsoon rainfall causes a reduction in groundnut yields ( [[#Xia--2014|Xia et al. 2014]] ; [[#Yang--2016|Yang et al. 2016]] ). SAI will increase the fraction of diffuse sunlight, which is projected to increase photosynthesis in forested canopy, but will reduce the direct and total available sunlight, which tends to reduce photosynthesis. As total sunlight is reduced, there is a net reduction in crop photosynthesis with the result that any benefits to crops from avoided heat stress may be offset by reduced photosynthesis, as indicated by a single statistical modelling study ( [[#Proctor--2018|Proctor et al. 2018]] ). SAI would reduce average surface ozone concentration ( [[#Xia--2017|Xia et al. 2017]] ) mainly as a result of aerosol-induced reduction in stratospheric ozone in polar regions, resulting in reduced downward transport of ozone to the troposphere ( [[#Pitari--2014|Pitari et al. 2014]] ; [[#Tilmes--2018|Tilmes et al. 2018]] ). The reduction in stratospheric ozone also allows more UV radiation to reach the surface. The reduction in surface ozone, together with an increase in surface UV radiation, would have important implications for crop yields but there is ''low confidence'' in our understanding of the net impact.

Few studies have assessed potential SRM impacts on human health and well-being. SAI using sulfate aerosols is projected to deplete the ozone layer, increasing mortality from skin cancer, and SAI could increase particulate matter due to offsetting warming, reduced precipitation and deposition of SAI aerosols, which would increase mortality, but SAI also reduces surface-level ozone exposure, which would reduce mortality from air pollution, with net changes in mortality uncertain and depending on aerosol type and deployment scenario ( [[#Effiong--2016|Effiong and Neitzel 2016]] ; [[#Eastham--2018|Eastham et al. 2018]] ; [[#Dai--2020|Dai et al. 2020]] ). However, these effects may be small compared to changes in risk from infectious disease (e.g., mosquito-borne illnesses) or food security due to SRM influences on climate (Carlson et al. 2022). Using volcanic eruptions as a natural analogue, a sudden implementation of SAI that forced the El Niño–Southern Oscillation (ENSO) system may increase risk of severe cholera outbreaks in Bengal ( [[#Trisos--2018|Trisos et al. 2018]] ; [[#Pinke--2019|Pinke et al. 2019]] ). Considering only mean annual temperature and precipitation, SAI that stabilises global temperature at its present-day level is projected to reduce income inequality between countries compared to the highest warming pathway (RCP8.5) ( [[#Harding--2020|Harding et al. 2020]] ). Some integrated assessment model

scenarios have included SAI ( [[#Arino--2016|Arino et al. 2016]] ; [[#Emmerling--2018|Emmerling and Tavoni 2018]] ; [[#Heutel--2018|Heutel et al. 2018]] ; [[#Helwegen--2019|Helwegen et al. 2019]] ; [[#Rickels--2020|Rickels et al. 2020]] ) showing the indirect costs and benefits to welfare dominate, since the direct economic cost of SAI itself is expected to be relatively low ( [[#Moriyama--2017|Moriyama et al. 2017]] ; [[#Smith--2018|Smith and Wagner 2018]] ). There is a general lack of research on the wide scope of potential risk or risk reduction to human health, well-being and sustainable development from SRM and on their distribution across countries and vulnerable groups ( [[#Honegger--2021a|Honegger et al. 2021a]] ; Carlson et al. 2022).

SRM may also introduce novel risks for international collaboration and peace. Conflicting temperature preferences between countries may lead to counter-geoengineering measures such as deliberate release of warming agents or destruction of deployment equipment ( [[#Parker--2018|Parker et al. 2018]] ). Game-theoretic models and laboratory experiments indicate a powerful actor or group with a higher preference for SRM may use SAI to cool the planet beyond what is socially optimal, imposing welfare losses on others although this cooling does not necessarily imply excluded countries would be worse off relative to a world of unmitigated warming ( [[#Ricke--2013|Ricke et al. 2013]] ; [[#Weitzman--2015|Weitzman 2015]] ; [[#Abatayo--2020|Abatayo et al. 2020]] ). In this context, counter-geoengineering may promote international cooperation or lead to large welfare losses ( [[#Helwegen--2019|Helwegen et al. 2019]] ; [[#Abatayo--2020|Abatayo et al. 2020]] ).

Cooling caused by SRM would increase the global land and ocean CO 2 sinks ( ''medium confidence'' ), but this would not stop CO 2 from increasing in the atmosphere or affect the resulting ocean acidification under continued anthropogenic emissions ( ''high confidence'' ) (AR6 WGI, Chapter 5).

Few studies have assessed potential SRM impacts on ecosystems. SAI and MCB may reduce risk of coral reef bleaching compared to global warming with no SAI ( [[#Latham--2013|Latham et al. 2013]] ; [[#Kwiatkowski--2015|Kwiatkowski et al. 2015]] ), but risks to marine life from ocean acidification would remain, because SRM proposals do not reduce elevated anthropogenic atmospheric CO 2 concentrations. MCB could cause changes in marine net primary productivity by reducing light availability in deployment regions, with important fishing regions off the west coast of South America showing both large increases and decreases in productivity ( [[#Partanen--2016|Partanen et al. 2016]] ; [[#Keller--2018|Keller 2018]] ).

There is large uncertainty in terrestrial ecosystem responses to SRM. By decoupling increases in atmospheric greenhouse gas concentrations and temperature, SAI could generate substantial impacts on large-scale biogeochemical cycles, with feedbacks to regional and global climate variability and change ( [[#Zarnetske--2021|Zarnetske et al. 2021]] ). Compared to a high CO 2 world without SRM, global-scale SRM simulations indicate reducing heat stress in low latitudes would increase plant productivity, but cooling would also slow down the process of nitrogen mineralisation, which could decrease plant productivity ( [[#Glienke--2015|Glienke et al. 2015]] ; [[#Duan--2020|Duan et al. 2020]] ). In high latitude and polar regions SRM may limit vegetation growth compared to a high CO 2 world without SRM, but net primary productivity may still be higher than pre-industrial climate ( [[#Glienke--2015|Glienke et al. 2015]] ). Tropical forests cycle more carbon and water than other terrestrial biomes but large areas of the tropics may tip between savanna and tropical forest depending on rainfall and fire ( [[#Beer--2010|Beer et al. 2010]] ; [[#Staver--2011|Staver et al. 2011]] ). Thus, SAI-induced reductions in precipitation in Amazonia and central Africa are expected to change the biogeography of tropical ecosystems in ways different both from present-day climate and global warming without SAI ( [[#Simpson--2019|Simpson et al. 2019]] ; [[#Zarnetske--2021|Zarnetske et al. 2021]] ). This would have potentially large consequences for ecosystem services (AR6 WGII, Chapters 2 and 9). When designing and evaluating SAI scenarios, biome-specific responses need to be considered if SAI approaches are to benefit rather than harm ecosystems. Regional precipitation change and sea salt deposition over land from MCB may increase or decrease primary productivity in tropical rainforests ( [[#Muri--2015|Muri et al. 2015]] ). SRM that fully offsets warming could reduce the dispersal velocity required for species to track shifting temperature niches whereas partially offsetting warming with SAI would not reduce this risk unless rates of warming were also reduced ( [[#Trisos--2018|Trisos et al. 2018]] ; [[#Dagon--2019|Dagon and Schrag 2019]] ). SAI may reduce high fire-risk weather in Australia, Europe and parts of the Americas, compared to global warming without SAI ( [[#Burton--2018|Burton et al. 2018]] ). Yet SAI using sulphur injection could shift the spatial distribution of acid-induced aluminium soil toxicity into relatively undisturbed ecosystems in Europe and North America ( [[#Visioni--2020|Visioni et al. 2020]] ). For the same amount of global mean cooling, SAI, MCB, and CCT would have different effects on gross and net primary productivity because of different spatial patterns of temperature, available sunlight, and hydrological cycle changes ( [[#Duan--2020|Duan et al. 2020]] ). Large-scale modification of land surfaces for GBAM may have strong trade-offs with biodiversity and other ecosystem services, including food security ( [[#Seneviratne--2018|Seneviratne et al. 2018]] ). Although existing studies indicate SRM will have widespread impacts on ecosystems, risks and potential for risk reduction for marine and terrestrial ecosystems and biodiversity remain largely unknown.

A sudden and sustained termination of SRM in a high CO 2 emissions scenario would cause rapid climate change ( ''high confidence'' ) (AR6 WGI, Chapter 4). More scenario analysis is needed on the potential likelihood of sudden termination ( [[#Kosugi--2013|Kosugi 2013]] ; [[#Irvine--2020|Irvine and Keith 2020]] ). A gradual phase-out of SRM combined with emissions reduction and CDR could avoid these termination effects ( ''medium confidence'' ) (MacMartin et al. 2014; [[#Keith--2015|Keith and MacMartin 2015]] ; [[#Tilmes--2016|Tilmes et al. 2016]] ). Several studies find that large and extremely rapid warming and abrupt changes to the water cycle would occur within a decade if a sudden termination of SAI occurred ( [[#McCusker--2014|McCusker et al. 2014]] ; [[#Crook--2015|Crook et al. 2015]] ). The size of this ‘termination shock’ is proportional to the amount of radiative forcing being masked by SAI. A sudden termination of SAI could place many thousands of species at risk of extinction, because the resulting rapid warming would be too fast for species to track the changing climate ( [[#Trisos--2018|Trisos et al. 2018]] ).

Public perceptions of SRM

Studies on the public perception of SRM have used multiple methods: questionnaire surveys, workshops, and focus group interviews ( [[#Burns--2016|Burns et al. 2016]] ; [[#Cummings--2017|Cummings et al. 2017]] ). Most studies have been limited to Western societies with some exceptions. Studies have repeatedly found that respondents are largely unaware of SRM ( [[#Merk--2015|Merk et al. 2015]] ). In the context of this general lack of familiarity, the publics prefer carbon dioxide removal (CDR) to SRM ( [[#Pidgeon--2012|Pidgeon et al. 2012]] ), are very cautious about SRM deployment because of potential environmental side effects and governance concerns, and mostly reject deployment for the foreseeable future. Studies also suggest conditional and reluctant support for research, including proposed field experiments, with conditions of proper governance ( [[#Sugiyama--2020|Sugiyama et al. 2020]] ). Recent studies show that the perception varies with the intensity of deliberation ( [[#Merk--2019|Merk et al. 2019]] ), and that the public distinguishes different funding sources ( [[#Nelson--2021|Nelson et al. 2021]] ). Limited studies for developing countries show a tendency for respondents to be more open to SRM ( [[#Visschers--2017|Visschers et al. 2017]] ; [[#Sugiyama--2020|Sugiyama et al. 2020]] ), perhaps because they experience climate change more directly ( [[#Carr--2018|Carr and Yung 2018]] ). In some Anglophone countries, a small portion of the public believes in chemtrail conspiracy theories, which are easily found in social media ( [[#Tingley--2017|Tingley and Wagner 2017]] ; [[#Allgaier--2019|Allgaier 2019]] ). Since researchers rarely distinguish different SRM options in engagement studies, there remains uncertainty in public perception.

Ethics

There is broad literature on ethical considerations around SRM, mainly stemming from philosophy or political theory, and mainly focused on SAI ( [[#Flegal--2019|Flegal et al. 2019]] ). There is concern that publicly debating, researching and potentially deploying SAI could involve a ‘moral hazard’, with potential to obstruct ongoing and future mitigation efforts ( [[#Morrow--2014|Morrow 2014]] ; [[#Baatz--2016|Baatz 2016]] ; [[#McLaren--2016|McLaren 2016]] ), while empirical evidence is limited and mostly at the individual, not societal, level ( [[#Burns--2016|Burns et al. 2016]] ; [[#Merk--2016|Merk et al. 2016]] ; [[#Merk--2019|Merk et al. 2019]] ). There is low agreement whether research and outdoors experimentation will create a ‘slippery slope’ toward eventual deployment, leading to a lock-in to long-term SRM, or whether it can be effectively regulated at a later stage to avoid undesirable outcomes ( [[#Hulme--2014|Hulme 2014]] ; [[#Parker--2014|Parker 2014]] ; [[#Callies--2019|Callies 2019]] ; [[#McKinnon--2019|McKinnon 2019]] ). Regarding potential deployment of SRM, procedural, distributive and recognitional conceptions of justice are being explored ( [[#Svoboda--2014|Svoboda and Irvine 2014]] ; [[#Svoboda--2017|Svoboda 2017]] ; [[#Preston--2018|Preston and Carr 2018]] ; [[#Hourdequin--2019|Hourdequin 2019]] ). With the SRM research community’s increasing focus on distributional impacts of SAI, researchers have started more explicitly considering inequality in participation and inclusion of vulnerable countries and marginalised social groups ( [[#Flegal--2018|Flegal and Gupta 2018]] ; [[#Whyte--2018|Whyte 2018]] ; [[#Táíwò--2021|Táíwò and Talati 2021]] ), including considering stopping research ( [[#Stephens--2020|Stephens and Surprise 2020]] ; [[#National%20Academies%20of%20Sciences%20Engineering%20and%20Medecine--2021|National Academies of Sciences Engineering and Medecine 2021]] ). There is recognition that SRM research has been conducted predominantly by a relatively small number of experts in the Global North, and that more can be done to enable participation from diverse peoples and geographies in setting research agendas and research governance priorities, and undertaking research, with initial efforts to this effect ( [[#Rahman--2018|Rahman et al. 2018]] ), noting that unequal power relations in participation could influence SRM research governance and have potential implications for policy ( [[#Winickoff--2015|Winickoff et al. 2015]] ; [[#Frumhoff--2018|Frumhoff and Stephens 2018]] ; [[#Whyte--2018|Whyte 2018]] ; [[#Biermann--2019|Biermann and Möller 2019]] ; [[#McLaren--2021|McLaren and Corry 2021]] ; [[#National%20Academies%20of%20Sciences%20Engineering%20and%20Medecine--2021|National Academies of Sciences Engineering and Medecine 2021]] ; [[#Táíwò--2021|Táíwò and Talati 2021]] ).

Governance of research and of deployment

Currently, there is no dedicated, formal international SRM governance for research, development, demonstration, or deployment (AR6 WGIII, Chapter 14). Some multilateral agreements – such as the UN Convention on Biological Diversity or the Vienna Convention on the Protection of the Ozone Layer – indirectly and partially cover SRM, but none is comprehensive and the lack of robust and formal SRM governance poses risks ( [[#Ricke--2013|Ricke et al. 2013]] ; [[#Talberg--2018|Talberg et al. 2018]] ; [[#Reynolds--2019a|Reynolds 2019a]] ). While governance objectives range broadly, from prohibition to enabling research and potentially deployment ( [[#Sugiyama--2018b|Sugiyama et al. 2018b]] ; [[#Gupta--2020|Gupta et al. 2020]] ), there is agreement that SRM governance should cover all interacting stages of research through to any potential, eventual deployment with rules, institutions, and norms ( [[#Reynolds--2019b|Reynolds 2019b]] ). Accordingly, governance arrangements are co-evolving with respective SRM technologies across the interacting stages of research, development, demonstration, and – potentially – deployment ( [[#Rayner--2013|Rayner et al. 2013]] ; [[#Parker--2014|Parker 2014]] ; [[#Parson--2014|Parson 2014]] ). Stakeholders are developing governance already in outdoors research; for example, for MCB and OAC experiments on the

Great Barrier Reef ( [[#McDonald--2019|McDonald et al. 2019]] ). Co-evolution of governance and SRM research provides a chance for responsibly developing SRM technologies with broader public participation and political legitimacy, guarding against potential risks and harms relevant across a full range of scenarios, and ensuring that SRM is considered only as a part of a broader portfolio of responses to climate change ( [[#Stilgoe--2015|Stilgoe 2015]] ; [[#Nicholson--2018|Nicholson et al. 2018]] ). For SAI, large-scale outdoor experiments even with low radiative forcing could be transboundary and those with deployment-scale radiative forcing may not be distinguished from deployment, such that [[#MacMartin--2019|MacMartin and Kravitz (2019)]] argue for continued reliance on modelling until a decision on whether and how to deploy is made, with modelling helping governance development.

<div id="14.4.5.1" class="h3-container"></div>

<span id="global-governance-of-solar-radiation-modification-and-associated-risks"></span>
==== 14.4.5.1 Global Governance of Solar Radiation Modification and Associated Risks ====

<div id="h3-22-siblings" class="h3-siblings"></div>

Solar radiation modification, in the literature also referred to as ‘solar geoengineering’, refers to the intentional modification of the Earth’s shortwave radiative budget, such as by increasing the reflection of sunlight back to space, with the aim of reducing warming. Several SRM options have been proposed, including stratospheric aerosol injection (SAI), marine cloud brightening (MCB), ground-based albedo modifications (GBAM), and ocean albedo change (OAC). SRM has been discussed as a potential response option within a broader climate risk management strategy, as a supplement to emissions reduction, carbon dioxide removal and adaptation ( [[#Crutzen--2006|Crutzen 2006]] ; [[#Shepherd--2009|Shepherd 2009]] ; [[#Caldeira--2017|Caldeira and Bala 2017]] ; [[#Buck--2020|Buck et al. 2020]] ), for example as a temporary measure to slow the rate of warming ( [[#Keith--2015|Keith and MacMartin 2015]] ) or address temperature overshoot ( [[#MacMartin--2018|MacMartin et al. 2018]] ; [[#Tilmes--2020|Tilmes et al. 2020]] ). SRM assessments of potential benefits and risks still primarily rely on modelling efforts and their underlying scenario assumptions ( [[#Sugiyama--2018a|Sugiyama et al. 2018a]] ), for example in the context of the Geoengineering Model Intercomparison Project GeoMIP6 ( [[#Kravitz--2015|Kravitz et al. 2015]] ). Recently, small-scale MCB and OAC experiments started to take place on the Great Barrier Reef ( [[#McDonald--2019|McDonald et al. 2019]] ).

SAI – the most researched SRM method – poses significant international governance challenges since it could potentially be deployed uni- or minilaterally and alter the global mean temperature much faster than any other climate policy measure, at comparatively low direct costs ( [[#Parson--2014|Parson 2014]] ; [[#Nicholson--2018|Nicholson et al. 2018]] ; [[#Smith--2018|Smith and Wagner 2018]] ; [[#Sugiyama--2018b|Sugiyama et al. 2018b]] ; [[#Reynolds--2019a|Reynolds 2019a]] ). While being dependent on the design of deployment systems, both geophysical benefits and adverse effects would potentially be unevenly distributed (AR6 WGI, Chapter 4). Perceived local harm could exacerbate geopolitical conflicts, not least depending on which countries are part of a deployment coalition ( [[#Maas--2012|Maas and Scheffran 2012]] ; [[#Zürn--2013|Zürn and Schäfer 2013]] ), but also because immediate attribution of climatic impacts to detected SAI deployment would not be possible. Uncoordinated or poorly researched deployment by a limited number of states, triggered by perceived climate emergencies, could create international tensions ( [[#Corry--2017|Corry 2017]] ; [[#Lederer--2018|Lederer and Kreuter 2018]] ). An additional risk is that of rapid temperature rise following an abrupt end of SAI activities ( [[#Parker--2018|Parker and Irvine 2018]] ; [[#Rabitz--2019|Rabitz 2019]] ).

While there is room for national and even sub-national governance of SAI – for example on research (differentiating indoor from open-air) ( [[#Jinnah--2018|Jinnah et al. 2018]] ; [[#Hubert--2020|Hubert 2020]] ) and public engagement ( [[#Bellamy--2017|Bellamy and Lezaun 2017]] ; [[#Flegal--2019|Flegal et al. 2019]] ) – international governance of SAI faces the challenge that comprehensive institutional architectures designed too far in advance could prove either too restrictive or too permissive in light of subsequent political, institutional, geophysical and technological developments ( [[#Sugiyama--2018a|Sugiyama et al. 2018a]] ; [[#Reynolds--2019a|Reynolds 2019a]] ). Views on governance encompass a broad range, from aiming to restrict to wanting to enable research and potentially deployment; in between these poles, other authors stress the operationalisation of the precautionary approach: preventing deployment until specific criteria regarding scientific consensus, impact assessments and governance issues are met ( [[#Tedsen--2013|Tedsen and Homann 2013]] ; [[#Wieding--2020|Wieding et al. 2020]] ). Many scholars suggest that governance arrangements ought to co-evolve with respective SRM technologies ( [[#Parker--2014|Parker 2014]] ), including that it stay at least one step ahead of research, development, demonstration, and – potentially – deployment ( [[#Rayner--2013|Rayner et al. 2013]] ; [[#Parson--2014|Parson 2014]] ). With the modelling community’s increasing focus on showing that, and in what ways, SAI could help to minimise climate change impacts in the Global South, the SRM governance literature has come to include considerations of how SAI could contribute to global equity ( [[#Horton--2016|Horton and Keith 2016]] ; [[#Flegal--2018|Flegal and Gupta 2018]] ; [[#Hourdequin--2018|Hourdequin 2018]] ).

Given that risks and potential benefits of SRM proposals differ substantially and their large-scale deployment is highly speculative, there is a wide array of concrete proposals for near-term anticipatory or adaptive governance. Numerous authors suggest a wide range of governance principles [[#Nicholson--2018|Nicholson et al. (2018)]] encapsulate most of these in suggesting a list of four: (i) Guard against potential risks and harm; (ii) Enable appropriate research and development of scientific knowledge; (iii) Legitimise any future research or policymaking through active and informed public and expert community engagement; (iv) Ensure that SRM is considered only as a part of a broader, mitigation-centred portfolio of responses to climate change. Regarding international institutionalisation, options range from formal integration into existing UN bodies like the UNFCCC ( [[#Nicholson--2018|Nicholson et al. 2018]] ) or the Convention on Biological Diversity (CBD) ( [[#Bodle--2014|Bodle et al. 2014]] ) to the creation of specific, but less formalised global fora ( [[#Parson--2013|Parson and Ernst 2013]] ) to forms of club governance ( [[#Bodansky--2013|Bodansky 2013]] ; [[#Lloyd--2014|Lloyd and Oppenheimer 2014]] ). Recent years have also seen the emergence of transnational non-state actors focusing on SRM governance, primarily expert networks and NGOs ( [[#Horton--2020|Horton and Koremenos 2020]] ).

Currently, there is no targeted international law relating to SRM, although some multilateral agreements – such as the Convention on Biological Diversity, the UN Convention on the Law of the Sea, the Environmental Modification Convention, and the Vienna Convention on the Protection of the Ozone Layer and its Montreal Protocol – contain provisions applicable to SRM ( [[#Bodansky--2013|Bodansky 2013]] ; [[#Jinnah--2019|Jinnah and Nicholson 2019]] ; [[#Reynolds--2019a|Reynolds 2019a]] ).

<div id="14.4.5.2" class="h3-container"></div>

<span id="carbon-dioxide-removal"></span>
==== 14.4.5.2 Carbon Dioxide Removal ====

<div id="h3-23-siblings" class="h3-siblings"></div>

Carbon dioxide removal (CDR) refers to a cluster of technologies, practices, and approaches that remove and sequester carbon dioxide from the ocean and atmosphere and durably store it in geological, terrestrial, or ocean reservoirs, or in products (Table 12.6). In contrast to SRM, CDR does not necessarily impose transboundary risks, except insofar as misleading accounting of its use and deployment could give a false picture of countries’ overall mitigation efforts. CDR is clearly a form of climate change mitigation, and as described in [[IPCC:Wg3:Chapter:Chapter-12|Chapter 12]] is needed to counterbalance residual GHG emissions that may prove hard to abate (e.g., from industry, aviation or agriculture) in the context of reaching net zero emissions both globally – in the context of Article 4 of the Paris Agreement – and nationally. CDR could also later be used for reducing atmospheric CO 2 concentrations by providing net negative emissions at the global level ( [[#Fuglestvedt--2018|Fuglestvedt et al. 2018]] ; [[#Bellamy--2019|Bellamy and Geden 2019]] ). Despite the common feature of removing carbon dioxide, technologies like afforestation/reforestation, soil carbon sequestration, bioenergy with carbon capture and storage, direct air capture with carbon storage, enhanced weathering, ocean alkalinity enhancement or ocean fertilisation are very different, as are the governance challenges. [[IPCC:Wg3:Chapter:Chapter-12|Chapter 12]] highlights the sustainable development risks associated with land and water use that are connected to the biological approaches to CDR. As a public good which largely lacks incentives to be pursued as a business case, most types of CDR require a suite of dedicated policy instruments that address both near-term needs as well as long-term continuity at scale ( [[#Honegger--2021b|Honegger et al. 2021b]] ).

CDR methods other than afforestation/reforestation and soil carbon sequestration have only played a minor role in UNFCCC negotiations so far ( [[#Fridahl--2017|Fridahl 2017]] ; [[#Rumpel--2020|Rumpel et al. 2020]] ). To accelerate, and indeed better manage CDR globally, stringent rules and practices regarding emissions accounting, measuring, reporting and verifying and project-based market mechanisms have been proposed ( [[#Honegger--2018|Honegger and Reiner 2018]] ; [[#Mace--2018|Mace et al. 2018]] ). Given their historic responsibility, it can be expected that developed countries would carry the main burden of researching, developing, demonstrating and deploying CDR, or finance such projects in other countries ( [[#Fyson--2020|Fyson et al. 2020]] ; [[#Pozo--2020|Pozo et al. 2020]] ). [[#McLaren--2019|McLaren et al. (2019)]] suggest that there is a rationale for separating the international commitments for net negative emissions from those for emissions reductions.

Specific regulations on CDR options have been limited to those posing transboundary risks, namely the use of ocean fertilisation. In a series of separate decisions from 2008 to 2013, Parties to the London Convention and Protocol limited ocean fertilisation activities to only those of a research character, and in 2012 the CBD made a non-legally-binding decision to do the same, further requiring such research activities to be limited scale, and carried out under controlled conditions, until more knowledge is gained to be able to assess the risks ( [[#GESAMP--2019|GESAMP 2019]] ; [[#Burns--2020|Burns and Corbett 2020]] ). In doing so they have taken a precautionary approach ( [[#Sands--2018|Sands and Peel, 2018]] ). The London Convention and Protocol has also developed an Assessment Framework for Scientific Research Involving Ocean Fertilisation ( [[#London%20Convention/Protocol--2010|London Convention/Protocol 2010]] ) and in 2013 adopted amendments (which are not yet in force) to regulate marine carbon dioxide removal activities, including ocean fertilisation.

<div id="14.5" class="h1-container"></div>

<span id="multi-level-multi-actor-governance"></span>